In Marielle Heller's fact-based film, the actress takes on her most dramatic role: an insightful look at the disgraced biographer, and one of McCarthy's favorite parts yet.

For her most dramatic film role to date, Melissa McCarthy followed a familiar path: a transformative role in a big-screen biopic about a singular (and very real) person. But as alcoholic forger Lee Israel in Marielle Heller’s “Can You Ever Forgive Me?,” McCarthy isn’t a particularly well-known character, nor does the film try to dull down the very rough edges of its subject. The film follows the downswing of her once-profitable career of a biographer to the stars, and McCarthy slips into the part of the brash and criminally clever Lee with ease and affection.

It’s smart subversion of on-screen expectations that embraces the real Lee while also letting McCarthy tap into darker material than she — and Hollywood — are used to seeing from actresses.

“I think there’s been far too much of the ‘perfect woman’ [on-screen], who I’ve personally never met,” she said, during a post-screening Q&A held at the SAG-AFTRA Foundation in Manhattan October 13, where she was joined by co-stars Richard E. Grant and Dolly Wells. “I don’t know anyone who actually knows this perfect woman. Perfect clothes, perfect home, perfect job, but, ‘Oh! can’t get a man,’ although there’s nothing humanly wrong with this person. I just don’t know what I would sink my teeth into and play with. I don’t have the skillset to do that. I’m not attracted to that.”

Even McCarthy’s lighter roles are rife with idiosyncrasies, from her puppy-stealing role in “Bridesmaids” to her rule-flouting cop in “The Heat.”

“As an avid people-watcher, probably to a creepy extent, I love people for their eccentricities and their flaws and their quirks and habits and tics,” she said. “I think it’s what makes people so interesting and riveting. All the people who are the closest to me in the world are just full of ’em, my best friends are probably clinically insane, and I love them for it.”

Those elements also help McCarthy bond more closely to her characters, and she suspects that audiences feel the same way.

“To play a woman like that, I really think it’s important and it’s certainly more enjoyable to play someone that I know or I have seen,” McCarthy said. “I feel like we have to represent real humans on the screen, because we’re trying to tell stories that I think tether us together as humans. To feel something for a character, you have to feel like, ‘I know that person’ or ‘I am a little bit that person’ or whatever it is.”

McCarthy’s affection for Israel started long before she was tapped for the film. Her husband, actor Ben Falcone, was cast in an earlier incarnation of the film that never quite took off, though he does appear in Heller’s film in his original role. (In 2015, Julianne Moore was briefly set to play the role; by 2016, McCarthy was on board.) McCarthy read that first script and was immediately in awe of it and Lee.

“I had such a strong reaction to it, and I just came out and said, ‘My God, this is one of the best scripts I’ve ever read, I’m so happy you’re doing this, why don’t I know who she is?,'” she said. “We talked about it for such a long time, and I thought, ‘What luck, you just don’t see characters like this, this is going to be amazing.’ And when it didn’t work out, I just couldn’t quite let her go.”

McCarthy felt that the character as crafted by screenwriters Nicole Holofcener and Jeff Whitty was, for all her outsized crimes and misdeeds, still very knowable. And once McCarthy knew her, she wasn’t able to get over her.

“I kept, probably very strangely, bringing it up every three weeks or so,” she remembered. “We would be talking about something, and I’d randomly be like, ‘I think because she’s fascinating! And I want to see the movie, I think other people [would, too],’ and my husband would be like, ‘What are you talking about? We weren’t talking about that,’ and I’d say, ‘I’m sorry, I was thinking about Lee.’ And then it kept happening. I was so enamored with her, and I had such a feeling of ‘I think I know her,’ I think I really am now responsible to tell her story, for some reason. Then I contacted the producers that had it and threw my name into the hat. … It worked.”

Fox Searchlight Pictures will open “Can You Ever Forgive Me?” on Friday, October 19.